Liquid crystal display device

ABSTRACT

A liquid crystal display device has a liquid crystal layer formed between first and second insulating substrates. A wiring layer, an insulation film and a first orientation layer are formed on the first substrate between it and the liquid crystal layer. A electrode layer and a second orientation film are formed on the second substrate between it and the liquid crystal layer. The wiring layer includes grooves along its peripheral portion which allow the insulation film to contact the first substrate, which promotes bonding and inhibits peeling of the insulation film from the wiring layer.

BACKGROUND OF INVENTION

The present invention relates to a liquid crystal display device, andmore particularly, to a liquid crystal display device which preventsstripping or corrosion of a wiring layer formed on a peripheral portionof an insulative substrate.

FIG. 1 is a schematic block diagram of a conventional active matrix typeliquid crystal display device. The pixel portion (display panel) 101comprises a plurality of scanning lines (gate wiring) G1-Gm, a pluralityof data lines (drain wiring) D1-Dm crossing orthogonally with the gatewiring G1-Gm, and pixels 102 provided at each of the intersections ofthe gate wirings and the drain wirings. A gate signal (a scanningsignal) from a gate driver 103 is applied to the gate wirings G1-Gm. Adata signal (a video signal) from a drain driver (data driver ) 104 isapplied to the drain wirings D1-Dm. The gate and drain drivers 103 and104 form a peripheral driver circuit 105. A liquid crystal displaydevice which comprises the driver 103 or 104 and the pixel portion 101formed on an insulative substrate 11 (FIG. 3) is generally called adriver built-in liquid crystal display device. The gate driver 103 maybe provided on both sides of the pixel portion 101. The drain driver 104may be provided on both sides of the pixel portion 101.

FIG. 2 is an equivalent circuit diagram of one of the pixels 102. Thepixel 102 comprise an TFT (Thin Film Transistor) 106 as a pixel driveelement, a liquid crystal cell LC and a supplementary capacitor (astorage capacitor or an additional capacitor) SC. The gate wiring Gn isconnected to the gate of the TFT 106, and the drain wiring Dn isconnected to the drain of TFT 106. The source of the TFT 106 isconnected to the supplementary capacitor SC and a display electrode(pixel electrode) 107 of the liquid crystal cell LC. The liquid crystalcell LC and the supplementary capacitor SC form a signal storageelement. An opposite electrode (common electrode) 108, which is arrangedopposite to the display electrode 107 of the liquid crystal cell LC,receives a voltage Vcom. The supplementary capacitor SC comprises astorage electrode 109 connected to the source of the TFT 106 and asupplementary capacitor electrode 110 to which a constant voltage VR isapplied. The opposite electrode 108 of the liquid crystal cell LC iscommon to all of the pixels 102. Static capacity is formed between thedisplay electrode 107 and the opposite electrode 108. The supplementarycapacitor electrode 110 may be alternatively connected to the adjacentgate wiring Gn+1.

FIG. 3 is a partial cross sectional view of the conventional displaypanel 101. A liquid crystal layer 13 is provided between opposing firstand second insulative substrates 11 and 12 which are preferably made oftransparent glass material. An aluminum alloy film 14 which forms awiring layer, a planarizing insulation film 15 preferably made ofacrylic resin and an orientation film 16 preferably made of polyimideresin are laminated on the first substrate 11. An opposite electrode 17(i.e., the opposite electrode 108) preferably made of ITO (Indium Tinoxide) and a second orientation film 18 preferably made of polyimideresin are laminated on the second substrate 12. A sealing material 19preferably an epoxy resin is provided between the insulative substrates11 and 12 to prevent leakage of the liquid crystal layer 13.Specifically, the sealing material 19 is provided between theorientation films 16 and 18 at the peripheral portions of the substrates11 and 12.

On the peripheral portions of the insulative substrates 11 and 12 towhich the sealing material 19 is provided, the aluminum alloy film 14 isformed all over the first insulative substrate 11. Adhesion strength ofthe aluminum alloy film 14 to the planarizing insulation film 15 islower than that of the planarizing insulation film 15 to the insulativesubstrate 11. Therefore, the planarizing insulation film 15 may easilypeel off the aluminum alloy film 14.

FIG. 4 is a partial cross sectional view of a second conventional liquidcrystal display device in which the aluminum alloy film 14 is formed asa lead wiring on the peripheral portion of the insulative substrate 11.The sealing material 19 is formed between the opposite electrode 17 andthe planarizing insulation film 15 to enclose liquid crystal layer 13and the orientation films 16 and 18 at the peripheral portions of theinsulative substrates 11 and 12.

A portion of the aluminum alloy film 14 forms a contact pad 20. Thecontact pad 20 may be made of a different material from the aluminumalloy film 14. The opposite electrode 17 is formed to extend to the edgeof the substrate 12, and an extended portion of the opposite electrode17 is connected to the contact pad 20 via a conductive material 21. Theconductive material 21 is preferably made of resin mixed with conductivematerial. The contact pad 20 receives a voltage Vcom via the inputterminal (not shown) of the lead wiring of the aluminum alloy film 14.The voltage Vcom is applied to the opposite electrode 17 via theconductive material 21.

Various input terminals (a power supply input terminal of voltage Vcomor VR, a power supply input terminal of the peripheral drive circuit 105and an input terminal of the data signal) are concentrated on the leadwiring of the aluminum alloy film 14. The arrangement of the inputterminals facilitates drawing wirings of an equipment when the liquidcrystal display device is mounted into various apparatus, such as apersonal computer, a word processor, an electronic notebook, or atelevision display monitor.

The area of the contact pad 20 provided on the peripheral portion of theinsulative substrate 11 is larger than the area necessary to connect theliquid crystal display device with an external circuit and is exposedout of the peripheral portion of the substrate 11. If the exposedportion of the contact pad 20 is exposed to air, it may cause corrosionof the aluminum alloy film 14 of the contact pad 20. Moreover, moistureor contaminants in the air may penetrate between the contact pad 20 andthe conductive material 21, adversely affecting the liquid crystal layer13 and the TFT 106.

It is an object of the present invention to provide a liquid crystaldisplay device which prevents stripping of the insulation film from thewring layer.

It is a secondary object of the present invention to provide a liquidcrystal display device which prevents corrosion of the wiring layer andpenetration of moisture or contaminants.

SUMMARY OF THE INVENTION

Briefly stated, the present invention provides a liquid crystal displaydevice. The liquid crystal display device includes first and secondinsulative substrates arranged opposite to each other. A liquid crystallayer is provided between the first and second insulative substrates. Asupplementary layer is located on the first insulative substrate. Thesupplementary layer has at least one slit formed near a peripheralportion thereof which exposes a portion of the first insulativesubstrate. A planarizing insulation film is located on the supplementarylayer and on the exposed portion of the first insulative substrate. Asealing material is provided between the planarizing insulation film andthe second insulative substrate to seal the liquid crystal layer.

The present invention provides a liquid crystal display device includingfirst and second insulative substrates arranged opposite to each other.A crystal layer is provided between the first and second insulativesubstrates. A wiring layer is located on the first insulative substrate.A contact pad is located on a peripheral portion of the first insulativesubstrate and electrically connected to the wiring layer. A commonelectrode is located on the second insulative substrate. A conductivematerial is provided between the first and second insulative substratesto electrically connect the common electrode and the contact pad. Aninsulation film is located on the wiring layer and covers around acontact portion between the contact pad and the conductive material.

Other aspects and advantages of the invention will become apparent fromthe following description, take in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention, together with objectives and advantages thereof,may best be understood by reference to the following description of thepresently preferred embodiments together with the accompanying drawingsin which:

FIG. 1 is a schematic block diagram of a conventional liquid crystaldisplay device;

FIG. 2 is an equivalent circuit diagram of a liquid crystal cell of theliquid crystal display device of FIG. 1;

FIG. 3 is a partial cross-sectional view of a conventional liquidcrystal display device;

FIG. 4 is a partial cross-sectional view of a second conventional liquidcrystal display device;

FIG. 5 is a partial cross-sectional view of a liquid crystal displaydevice according to a first embodiment of the present invention;

FIG. 6 is a schematic diagram of an insulative substrate of the liquidcrystal display device of FIG. 5;

FIG. 7A is a partial cross-sectional view of a liquid crystal displaydevice according to a second embodiment of the present invention;

FIG. 7B is a partial cross-sectional view of the liquid crystal displaydevice along line I--I of FIG. 7A;

FIG. 7C is a partial cross-sectional view of the liquid crystal displaydevice along line II--II of FIG. 7A;

FIG. 8 is a partial cross-sectional view of a liquid crystal displaydevice according to a third embodiment of the present invention; and

FIG. 9 is a partial cross-sectional view of a liquid crystal displaydevice according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, like numerals indicate like elements throughout.Referring to FIG. 5, a liquid crystal display device 200 according to afirst embodiment of the present invention includes a plurality of slits14a formed on an area of the aluminum alloy film 14 corresponding to theperipheral portion (the sealing area) of the first insulative substrate11 on which the sealing material 19 is provided. More specifically, thesealing material 19 is provided at the peripheral portion of the firstand second transparent insulative substrates 11 and 12. A plurality ofprojections 14b preferably made of the aluminum alloy film are formed ona seal forming area of the first substrate 11 below the sealing material19.

The surface of the first substrate 11 is exposed by the slits 14a cut inthe aluminum alloy film 14. Accordingly, the exposed surface (the areaof each slit 14a) of the first substrate 11 is directly contacted withthe planarizing insulation film 15. Thus, the contacting area betweenthe first substrate 11 and the planarizing insulation film 15 isincreased in order to prevent peeling off of the planarizing insulationfilm 15 from the aluminum alloy film 14 in the seal forming area of theperipheral portion of the first substrate 11. As a result, defectivedisplaying of images on the display device 200 caused by peeling-off ofthe film 15 is prevented.

In the liquid crystal display device 200, as shown in FIG. 6, theprojections 14b form lead wirings for the gate driver 103 and the draindriver 104.

A liquid crystal display device 210 according to a second embodiment ofthe present invention, as shown in FIGS. 7A-7C, has a portion of thesurface of the aluminum alloy film 14 excluding a first contact pad 20and one or more second contact pads 22 covered by the insulation film 15near the edge of the first substrate 11. The first contact pad 20 iselectrically connected to the opposite electrode 17 via the conductivematerial 21, and the second pads 22 are electrically connected anexternal circuit(not shown). In other words, the covered surface of thealuminum alloy film 14 is not used for the external connection.Therefore, the covered surface of the aluminum alloy film 14 is notexposed to air so that the aluminum alloy film 14 is protected fromcorrosion. In the second embodiment, a portion of the insulation film 15is eliminated to ensure a good connection between the contact pad 20 andconductive material 21. The insulation film 15 is preferably made ofsilicon oxide, SOG (Spin On Glass), various silicate glass (BSG, PSG, orBPSG), silicon nitride or various kinds of organic insulating film.Since the contacting faces between the contact pad 20 and the conductivematerial 21 are protected by the insulation film 15, the possibilitythat moisture or contaminants in air penetrating into the contactingfaces is eliminated. That is, moisture or contaminants are preventedfrom penetrating the liquid crystal layer 13 or the TFT 106 provided onthe first insulative substrate 11. As a result, the reliability of theliquid crystal display device 210 is improved.

Referring to FIG. 8, a liquid crystal display device 220 according to athird embodiment of the present invention is characterized by thefollowing four structural features:

(1) A plurality of spherical particles (conductive beads) 31 areprovided instead of the conductive material 21. The surface of each bead31 is preferably coated with a conductive material, such as gold (Au).Such beads 31 are commercially available (e.g., "Microperl" manufacturedby Sekisui-Kagaku of Japan).

More specifically, the opposite electrode 17 (108) of the liquid crystalcell LC is extended to the edge of the second insulative substrate 12and the extended portion of the opposite electrode 17 is connected tothe contact pad 20 via the conductive beads 31. The contact pad 20receives a voltage Vcom via the input terminal (not shown) of the leadwiring of the aluminum alloy film 14. The voltage Vcom is applied to theopposite electrode 17 via the conductive material coated on the surfaceof each conductive bead 31.

(2) A portion of the contact pad 20 which is exposed at the edge of thefirst insulative substrate 11 and is not used to connect with theexternal circuit is covered by the insulation film 15. That is, theportion of the contact pad 20 unnecessary for the external connection isnot exposed.

(3) Contact holes 32 are provided at positions corresponding to theconductive beads 31, respectively. The diameter of the contact hole 32is preferably large enough not to allow movement of the conductive bead31 when it is fit into the hole 32. That is, each conductive bead 31 isfixed when it is fit into the contact hole 32.

(4) A resin 33 is filled in the space in which the conductive beads 31are provided between the first and second transparent insulativesubstrates 11 and 12. The resin 33 is preferably moisture resistant.Therefore, contact portions between the contact pad 20 and theconductive beads 31 are protected by the resin 33 and the insulationfilm 15.

Referring to FIG. 9, a liquid crystal display device 230 according to afourth embodiment of the present invention is different in the followingpoints from the third embodiment of FIG. 8:

(1) A transparent conductive film or an ITO film 41 is formed on thecontact hole 32 and inter-layer insulating film 15 at the edge of thefirst insulative substrate 11. That is, the opposite electrode 17 isconnected to the contact pad 20 via the conductive beads 31 and the ITOfilm 41. The voltage Vcom applied to the contact pad 20 is applied tothe opposite electrode 17 via the ITO film 41 in the contact hole 32 andthe conductive material coated on the surface of the respectiveconductive beads 31. The ITO film 41 is preferably formed simultaneouslywith the display electrode (FIG. 2) of the liquid crystal cell which ismade of the ITO film. The ITO film 41 is more resistant to corrosionthan the aluminum alloy film 14 and improves corrosion resistance.Further, the ITO film 41 improves contact between the conductive beads31 and aluminum alloy film 14.

It should be apparent to those skilled in the art that the presentinvention may be embodied in many other specific forms without departingfrom the spirit or scope of the invention. Particularly, it should beunderstood that the invention may be embodied in the following forms.For example, the aluminum alloy film 14 may be replaced by a film madeof any metal with a high melting point. The planarizing insulation film15 may be formed by silicone oxide, SOG (Spin On Glass), varioussilicate glass (BSG, PSG or BPSG), silicon nitride or various kinds oforganic insulative material. Therefore, the present examples andembodiments are to be considered as illustrative and not restrictive andthe invention is not to be limited to the details given herein, but maybe modified within the scope and equivalence of the appended claims.

What is claimed is:
 1. A liquid crystal display device, comprising:firstand second insulative substrates arranged opposite to each other; aliquid crystal layer provided between the first and second insulativesubstrates; a supplementary layer located on the first insulativesubstrate, the supplementary layer having at least one slit formed neara peripheral portion thereof which exposes a portion of the firstinsulative substrate; a planarizing insulation film located on thesupplementary layer and on the exposed portion of the first insulativesubstrate; and a sealing material provided between the planarizinginsulation film and the second insulative substrate to seal the liquidcrystal layer.
 2. The liquid crystal display device of claim 1, whereinthe supplementary layer includes at least two projections provided onboth sides of the at least one slit.
 3. The liquid crystal displaydevice of claim 1, wherein the supplementary layer comprises aconductive layer.
 4. The liquid crystal display device of claim 3,wherein the conductive layer forms a portion of the signal wiring of theliquid crystal display device.
 5. The liquid crystal display device ofclaim 3, wherein the conductive layer comprises an aluminum alloy layer.6. The liquid crystal display device of claim 1, wherein thesupplementary layer comprises an aluminum alloy layer.
 7. The liquidcrystal display device of claim 1, wherein the planarizing insulationfilm comprises an acrylic resin film.